The present disclosure relates generally to data communications. More particularly, the present disclosure relates to floating frame timing circuits for network devices.
Various protocols defined by standards bodies like IEEE allow end stations to exchange timing information across various nodes within a network of devices. This timing information can include providing a consistent time of day for all nodes, accurate clock synchronization mechanisms, and the like.
Conventional Ethernet as defined by the IEEE 802 standards body is asynchronous in nature, that is, end stations don't employ a common time base or even a concept of time. However, several applications exist that could benefit from isochronous Ethernet communications, for example media streaming applications like Internet Protocol Television (IPTV), high-definition audio and video consumer appliance traffic, and the like.
To enable such applications, the IEEE 802.1 standards body is developing a new standard to accommodate exchange of timing and synchronization information with respect to stations or nodes connected via Ethernet. To accommodate isochronous operation, the new IEEE 802.1AS standard under development specifies the use of a Precision Time Protocol (PTP), an industrial automation standard (IEEE 1588), in conjunction with existing Ethernet protocols.
To attain the timing accuracy required by PTP, measurements of frame arrival and departure times are preferably made using hardware timing circuits. However, because network devices currently provide multiple ports, multiple interfaces per port, or both, the number of timing circuits needed to obtain these measurements for each interface can be large, thereby increasing the cost and complexity of the devices.